Am 03.07.2015 um 05:08 schrieb Nekar Xenos:

>>> If you are using fresnel, is it valid (from a PBR point of view) to even
>>> scale the results using a maximum reflection other than 1?
>>
>> Absolutely - if, for instance, your surface is littered with
>> non-specular material at a microscopic level. Fine rust on iron steel,
>> for instance, or a thin coating of dust.
>>
>> In those cases it might be better, however, to use an average of two
>> materials.
>>
>
> What about plastic? It reflects, but it's not highly reflective. I don't
> think I would go higher than 0.5 maximum reflection on plastic.

For plastics - and actually any material that's neither metallic nor 
coated - I think heavily blurred reflections and a well-chosen ior are 
the key, not reducing the reflection maximum.

With a high ior, the maximum reflection only occurs when viewing the 
material almost edge-on. And with blurred reflections, even there the 
maximum isn't truly achieved, as the effective reflection brightness is 
tuned down by averaging in reflections at a less shallow effective angle.

BTW, the ior of most plastics is in the range from 1.5 to 1.6.

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